Snap action switch



Nov. 20, 1956 V3. M. HAUSLER 2,771,527

SNAP ACTION swITcH Filed July 16, 1954 Inventors 4o GQEM. H ler, b HisOPT-seg.

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United States Patent O SNAP ACTION SWITCH George M. Hausler,Schenectady, N. Y., assignor to .Gen-

eral Electric Company, a corporation of New York Application July 16,1954, Serial No. 443,823

7 Claims. (Cl. 200--67) This invention relates to improvements inelectrical switches and more particularly to that type of electricalswitch having a snap action operating characteristic.

An electric switch is frequently required to operate with rapid andpositive contact movement although controlled by an actuating means,such as a pressure, fluid level or temperature responsive device, whichtravels only through a small distance at a very slow rate. To prevent anundesirable condition of contact arcing, it is desirable to provide aswitch in which a high contact pressure will be maintained up to themoment of operation whereupon the switch contacts will open or closewith a snap action.

, Accordingly, it is an object of my invention to provide an improvedelectrical switch having a mechanism in which irreversible motion isinitiated by an actuating means before positive Contact pressure isreduced to zero whereupon snap operation occurs regardless of thedistance or rate of movement of the actuating means.

It is a further object of my invention to provide an improved snapaction switch with a minimum number of operating parts which is small insize, inexpensive to manufacture, yet durable, reliable and highlysensitive.

A still further object of my invention is to provide a snap actionswitch with a simplied mechanism particularly well suited for doublepole, single throw switching applications. v

Another object of my invention is to.provide a snap action switchoperated by a movable actuating means wherein the switch is readily andconveniently changeable from a switch with normally open contacts to amovable switch member formed at least in part of resilient springmaterial. Such switch member comprises a pair of resilient outer tensionarms disposed in flatwise coplanar parallel spaced apart relation andxedly mounted at like ends, a pair of compression arms in intermediateparallel spaced apart relation each flexibility connected for relativepivotal movement at one end to a free end of one outer tension arm andjoined together at their other ends, and a parallel central tension armconnected at one end to the junction of the compression arms. Thiscentral tension arm may be an integral part of the switch member andhereafter will be referred to as a part thereof, but it is preferably aseparate tension spring. A movable switch contact is mounted on the freeend of each outer tension arm in cooperating relationship with one of apair of stationary switch con- The portion of the switch memberinterconnecting the compression arms is preferably of insulatingmaterial to electrically isolate the two movable switch contacts therebyrendering the switch suitable for double pole application.

An actuating member is connected to the orderend of the central tensionarm and is movable in a transverse `path to carry the tension centerlineof the central tension arm across thercompression centerline of the com-I,

ICC

pression arms at which point the interconnecting portion will snap fromone to the other of two preselected positions. This snap action-willcause the compression centerline of the compression arms to cross thetension centerline of the outer tension arms at which. point the freeends of the outer tension arms will move with snap action from one tothe other of two preselected positions, one of which is defined by thestationary switch contacts. Thus, the movable switch contacts arecarried with a snap action Vinto or out of engagement with thestationary switch contacts independently of the rate of movement of theactuating member.

The movable switch member is located approximately on the centerline ofan enclosure, and the enclosure is suitable for mounting with its coverfacing either up or down with respect to the actuating member.Therefore, it is possible to mount the enclosure in alternate positionswhereby the switch contacts will be either normally open or normallyclosed as desired.

My invention will be better understood and further objects andadvantages will be apparent from the following detailed descriptiontaken in conjunction with the accompanying drawing, in which Fig. 1 isan overall elevational view of the enclosure for my improved snap actionswitch mechanism; Fig. 2 is a plan view of the switch mechanism shownwith the enclosing cover removed; Fig. 3 is an elevational view of theswitch enclosure with the near Vside broken away to more clearlyindicate the positions of switch components with the switch contactsclosed; and Fig. 4 is another elevational View similar to Fig. 3 exceptwith the switch contacts in their open position.

Referring now to Fig. l, an enclosure 11 comprising a cover 12 and abase 13 provides a housing for the snap action switch mechanism of myinvention. holes 14 are provided through enclosure 11 and accommodatebolts (not shown) which fasten the cover 12 to the base 13 and alsofasten the enclosure 11 to a suitable supporting frame .(not shown). Theenclosure 11, is constructed preferably of a molded plastic insulatingmaterial.

As shown in Fig. 2, Vthe snap action switch mechanism mounted insideenclosure 11 comprises a thin, flat movable switch member 15, a pair ofxed switch contacts 17, and suitable clamping type terminals 18 forterminating four electrical connectors (not shown) entering enclosure 11from a remote circuit to be controlled by the switch. A pair ofcooperating movable switch contacts 16 are carried by switch member 15.

Each terminal 18 comprises an I-shaped post 19, a clamp- -ing member 20encircling the post 19 and a clamping screw 21, as shown in the drawing.Each post 19 extends in a transverse direction. A pair of holes 22,.onein cover 12 and one in base 13,.is associated with each post, each holebeing located so that an electrical conductor entering enclosure 11through the hole will extend parallel to and immediately adjacent onesurface of the associated post 19. The clamping member 20 encircles notonly the post 19 but also the conductor, and by means of the clampingscrew 21 which is threaded through the clamp- .ing member 20 to engagethe opposite surface of post A pair of spaced apart elongated arms ofwhich three are tension arms and two are compression arms. A pair ofoutside arms 25, longitudinally stressed in tension, are constructed ofsuitable strips of current conducting, resilient material. A fixed end26 of each arm 25 is anchored to base 13 by a rivet 27, and a connectionis made at this end to a terminal 18 having the construction describedabove. Due to the resiliency of arm 25, the other end 28 of each outsidetension arm is free to move in a transverse direction pivotally aboutthe Iixed end 26. From free end 28 a portion of the resilent strip isdisposed parallel to arm 25 on its inward side, and the resulting Ucon'riguration forms a exible connection 29.

The movable switch contacts 16 are mounted on the outside tension arms25 of the movable switch member 15. Each contact 16 is located at thefree end 28 of an arm 25 where it faces a sta-tionary contact 17 incontact making and breaking relation. Clockwise pivotal movement of thefree end 28 of arm 25 about fixed end 26, as viewed in Fig. 3, willcarry contact 16 into engagement with contact 17. Stationary ycontact 17thereby serves as a stop for the free end 28 when moved in thisdirection. Upon counterclockwise pivotal motion of the yfree end 28, thecooperating contacts 16 and 17 will disengage. As can be seen in Fig. 4,a stop 30 formed by aprotrusion of cover 12 engages connection 29 tostop the counterclo'ckwise movement of free end 28. Operation of th'eswitch mechanism will open and close the remote electrical circuitconnected to cooperating movable and stationary switch contacts by meansof the terminals 18 connected respectively to the fixed end 26 oftension arm 25 and to the stationary contact 17.

Two intermediate arms 31 longitudinally stressed in compression aredisposed inwardly adjacent to the two outside tension arms 25. Each arm31 is formed from a different leg 'of a unitary U-shaped strip ofinsulating material 32. The open end of each leg is connected by a pairof rivets 33 to the inwardly disposed end of a different resilent strip25. A closed end portion 34 of each leg is `free to move in a transversedirection pivotally about the flexible connection 29 formed at free end28 of each outside tension arm 25. To limit the movement of end 34 ofeach compression arm 31, two pairs of stops, 35 and 36, are formed byprojecting portions of the cover 12 and base 13, respectively, and aredisposed on opposite sides of the ends 34, as shown in Figs. Y3 and 4.To .insure `that 'both movable switch contacts 16- operate in unison tomake and break contact with the stationary switch contacts 17substantially simultaneously, the uii'itary U-shaped strip 32 comprisingpart of both compression arms 31 is constructed -of relatively rigidmaterial. Thus the flexible connections 2-9 formed at the free ends 28of both outside tension arms 25 are rigidly interconnected, and movementof one will be translated to c'orresponding movement of the other.

The double pole 'construction of my snap action switch is a result ofthe 'insulating characteristic of the unitary strip 32. Thisinterconnecting member electrically insulates one outside tension armfrom tlie other outside tension arm and thereby insulates connectionsmade to o ne movable switch contact 16 and its cooperating stationaryswitch contact 17 from connections made to the other movable andstationary switch contacts.

A first snap action system is formed by the coaction of 'anintermedia-te compression arm 31 and an outside tension arm 25. Thestress arm 25 in tension. Whenever the centerlines of 'the forces inthese two arms are .in alignment, the compression and tension forces areequal and opposite and all of the compression force is used to stressthe tension arm. However, when the centerline' of these two forces arenot aligned, the compression force is opposed at flexible connection 29by an Vvequal Vforce having two components; a longitudinal component inthe plane of arm 25 stressing this tension arm, and a ltransversecomponent perpendicular to the plane of tension arm 25 applying a torqueat 29, with tension arm 25 forming the moment arm, tending to pivot theconnection 29 about the fixed end 26 of arm 25. Thus, as shown in Fig.3, with end 34 of compression arm 31 above the tension centerline oftension arm 25, a transverse component of force at connection 29 appliesa positive pressure to hold movable contact 16 in engagement withstationary contact 17. Should compresison arm 31 be pivotedcounterclockwise about the flexible connection 29, the compressioncenterline of arm 34 will cross the tension centerline of arm 25whereupon the component of transverse force at 29 will pass through zeroand change direction to move connection 29 with a snap actioncounterclockwise about fixed end 26 of arm 25 to its upper posi-tiondetermined by engagement with stop 30, shown in Fig. 4.

To control the movement of the closed end portion 34 of each compressionarm 31, a third tension arm 37 is provided. One end of tension arm 37 ispivotally connected to a mid-portion 38 of the closed end of the U-shaped strip 32 interconnecting the pair of compression arms 31. In theillustrated embodiment of my invention this central tension arm of themovable switch member comprises a tension spring. The other end 39 ofcentral tension arm 37 is adapted to be connected to an actuating means.The actuating means is movable in a transverse path and supplies asuicient force to longitudinally stress central arm 37 in tension.Although the actuating means may be of any suitable type, for thepurposes of this specification it has lbeen illustrated in Fig. l ascomprising an Lshaped rigid actuating member 40 pivotally connected atone end to a fixed pivot 4l. The other end 42 is connected to end 39 ofthe central tension arm 37. A pair of fixed stop pins 43 and 44 definethe upper and lower limits respectively of the transverse travel of theactuating member 40, and a bias spring 45 normally biases the member 40to its lower position. A plunger 46 acts against the force of the biasspring 45 to pivotally move member 40 to its upper position. Plunger 46may be operated by any suitable means, such as, for example, a pressureresponsive diaphragm, not shown; and it will be assumed that its rate ofmovement is exceptionally slow. The force in the central tension arm 37,as supplied by the tension spring in combination with the actuatingmeans, provides the source of force for the entire movable switch member15 to stress both the compression arms 31 and the outside .tension arms25.

A second snap action system is formed by the coaction of thecentraltension arm 37 and a compression arm 31. The tension arm 37supplies a force at the pivotal connection 38 to stress arm 31 incompression. Whenever the centerlines of the forces in these two armsare in alignment, the tension and compression forces are equa-l andopposite and all of the tension force is used to compress arm '31.However, whenever the centerlines of these two forces are not inalignment, the tension force is opposed at connection '38 by an equalforce fhaving two components; a longitudinal component in the plane ofarm 31 stressing this compression arm, and a transverse componentperpendicular to the plane of the'com- .pression arm 31 applying atorque at connection 38, compression arm 31 forming the moment arm,

tending to pivot connection 38 vabout the ilexible connection l29.

lThus, as shown in Fig. 3, with end 39 of central tension -force atconnection 38 will pass through zero and change direction to urge theclosed end 34 of arm 31 counterclockwise about iiexible connection 29with a snap action to its lower position as determined by engagementwith stop36, shownin Fig. 4.'

In effect, the movable switch member 15 described above comprises a pairof ilat integral U-shaped strips of resilient material having along anda short arm and arranged on coplanar side by side relation with theshort arms 31 disposed inwardly and interconnected at their open ends.The outer arms v25 are xedly mounted at their open ends. A spring means37 is connected to the common ends of the inner arms to place the innerarms in compression and the outerarms in tension thereby to provideseparate overcenter operation of the inner arms with respect to thespring means and with respect to the outer arms.

Movement of the actuating member 40, as controlled by movement ofplunger 46, may be very slow. However, it need only carry end 39 ofcentral tension arm 37 through a well dened position in `which thetension centerline of arm 37 crosses thel compression centerline ofcompression arms 31 to produce a snap action opening or closing ofswitch contacts 16 and 17. Upon reaching this `position of alignment,the closed end portions 34 of compression arms 31 will snap from one tothe other of their alternate positions defined by stops 35 and 36, asdescribed above for the second snap` action system. As a result,compression arms 31 will pass through a position wherein theircompression centerline is in alignment with the tension centerline ofthe outside tension arms 25,`and the flexible connections 29 will snapfrom one to the other of their alternate positions defined by stops 30and stationary contacts 17, as described above for the irst snap actionsystem. This sequence of snap actions takes place extremely fast and isvirreversible. The former must be underway before the latter can occur.Therefore, the position of the movable switch contacts 16 will bemaintained with positive pressure until after the former snap` action`has been initiated. The actuating member 40, having initiated the formersnap action, can exercise no further control over the switch mechanismuntil after the sequence of snap actions has been completed. i

Contact bounce is substantially eliminated in `this snap action switch.Whenever the free end 28 of each outside tension arm 25 is in either ofits alternate positions as holes 22 in cover 11. Electrical connectorsentering enclosure 11 through 12, for example, and clamped to terminals18 can be loosened and removed while the enclosure 11 is reversed, afterwhich they can be reinserted through holes 22 in the base 13 andreclamped.

While I have shown and described a preferred form of my invention by wayof illustration, many modifications will occur to those skilled in theart. I therefore contemplate by the appended claims to cover all suchmodiflcations as fall within the true spirit and scope of my invention.y

What I claim as new and desire to secure by Letters Patent of the UnitedStates is: v

1. A snap action switch comprising a pair ,of parallel spaced apartelongated compression arms each having opposite first and second endportions which are movable in a transverse direction, relatively rigidmeans interconnecting the first end portions of said compression arms,tirst and second parallel spaced apart tension arms disposed laterallyadjacent said compression arms and each l including a resilient'elongated portion having one end delined by the engagement of contacts16 and 17 or by 4 connection 29 engaging stop 30, a transverse componentof force is present to apply a positive pressure to hold free end 28 inthat position. This transverse force, together with the low inertia ofsmall and light weight moving parts, enables the switch mechanism tooperate with substantially no contact bounce. Similarly, there issubstantially no bounce at the closed end 34 of each compression arm 31upon operation thereof.

To enable the double pole snap action switch to be operated as either anormally open or normally closed switch, the location of the switchmechanism inside enclosure 11 is carefully selected so that the positionof the plane of the movable switch member 15, when in an unstressedcondition, will correspond approximately with the centerline of theenclosure 11. With the-enclosure 11 located as shown'in the drawing, andthe actuating member 40 normally biased to its lower position, theswitch contacts 16` and 17 will be normally open, as illustrated in Fig.4. Upward movement of the actuating member 40 will cause movable switchcontact 16 to snap into engagement with the stationary switch contact17. However, itis possible to turn over the enclosure 11 and mount itwith cover 12 down, base 13 up. In this position, not shown, thenormally biased downward actuating member 40 will result in normallyclosed switch contacts 16 and 17, and upward movement of member 40 willcause the movable switch contact 16 to snap out of engagementwith'stationary-contact 17. It is a relatively easy matter to reversethe position of the enclosure tlexibly connected to the second endportion of ,one of said compression arms and having the other end xedlymounted, each of said first and second tension arms forming a snapaction system with the associated llexibly connected compression arm,whereby the second end portions of said compression arms will move withsnap action whenever the compression centerline of said compression armsis moved kthrough a position of alignment with the tension centerline ofsaid rst and second tension members in response to transverse movementof said interconnecting means, a third elongated tension arm disposedintermediate and in parallel relationship to said compression arms andhaving one end movable in a transverse direction and theother endpivot-ally connected to said interconnecting `means to form with saidcompression arms another snap action system, whereby saidinterconnecting means will move with snap action whenever the tensioncenterline of said third tension arm is moved through a position ofalignment with the compression centerline of said compression arms inresponse to transverse movement of said one end of said third tensionarm, a movable actuating member connected to said one end of said thirdtension arm and disposed to apply tensile stress to said third tensionarm while moving in a transverse path thereby to `actuate thesnap actionsystems, a pair of movable switch contacts mounted for movement with thesecond end portions of said compression arms, and ya pair of stationaryswitch contacts xedly mounted in cooperating relationship with saidmovable switch contacts.

2. A snap action switch comprising a thin, fiat movable switch memberhaving an outer pair of substantially parallel tension members eachhaving a resilient longitudinal portion extending between a fixed endand a free end, a pair of intermediate parallel compression members eachhaving one end pivotally connected to a different said free end, meansinterconnecting the other ends of both said compression members, Iand acentral parallel tension member having one end pivotally connected tosaid interconnecting means; a movable actuating member connected to theother end of said central tension member and disposed to apply tensilestress to said central tension member while moving, in a pathsubstantially perpendicular to the plane of said movable switch member;a pair of movable switch contacts supported by said switch member nearsaid free ends and movable with snap action in a direction substantiallyperpendicular to the plane of said movable switch member in response tomovement of the tension centerline of said central tension memberthrough a position of alignment with the compression centerline of saidpair of compression members;

3. A snap action switch comprising a stationary support member, a thin,flat movable switch member 'having a plurality of Substantially parallelspaced apart interconnected elongated arms including three tension armsand a pair of intermediate compression arms, a relatively rigidinsulating member interconnecting like ends of said compression arms, anoutside pair of said tension arms each having a resilient elongatedportion with a fixed end mounted on said support member and a free endflexibly connected to the end of the Iadjacent compression arm oppositesaid interconnected end and movable in a transverse direction betweentwo preselected positions, a pair of movable switch contacts eachmounted on said switch member near a different said free end, a pair ofspaced apart fixed switch contacts mounted on said support member incooperating relationship with said movable switch contacts, first andsecond stops Ymounted on said support member in spaced apart relationopposing said pair of fixed switch contacts to define therewith saidpreselected positions of said free end, said outside tension arms andsaid compression arms forming a first snap action system actuated .bytransverse movement of said insulating member to move the compressioncenterline of said compression arms through a position of alignment withthe tension centerline of said outside tension arms whereupon said freeend will snap from one to the other said preselected positions, thirdand fourth opposing stops mounted on said support member in spaced apartrelation on opposite sides of said insulating member to limit thetransverse travel thereof, a central said tension arm having one yendpivotally connected to said insulating member and forming with saidcompression arms a second snap action system actuated by transversemovement of the other `end of said central tension arm to move thetension centerline of said central tension arm through a position ofalignment with the compression centerline of the compression armswhereupon said insulating member will move with snap action between saidopposing stops, land a movable actuating member connected to said otherend of said central tension .arm and movable in a transverse path toapply tension to said central tension arm and to move said centraltension arm thereby to actuate said second snap action system whereuponsaid irst snap action system will operate.

4. A snap action switch comprising an enclosure having a height dened byopposing substantially dat parallel top and bottom surfaces, a movableswitch member located Within said enclosure having a plurality ofparallel spaced apart interconnected tension and compression membersgenerally defining a plane parallel to said top and bottom surfaces, arst said tension member having a resilient longitudinal portion with afixed end connected to `said enclosure and a free end movable in atransverse direction, a movable switch contact supported by said switchmember near said free end of said first tension member, a fixed switchcontact mounted in said enclosure in cooperating relationship with saidmovable switch contact, a said compression member having one endpivotally connected to said free end of said first tension member, asecond tension member having one end pivotally connected to the oppositeend of said compression member, and a biased movable actuating memberreleasably connected to the opposite end of said second tension memberin tension applying relationship and movable against its bias in atransverse path to move the tension centerline of said second tensionmember through a position of alignment with the compression centerlineof said compression member thereby to actuate snap ac- .tion of saidfree end to carry said movable contact into or out of engagement withsaid fixed contact, said position of alignment approximately bisectingthe height of said enclosure between said top and bottom surfaces topermit the reversing of the direction of snap movement of said movableswitch contact in response to movement of said actuating member againstits bias by reversing said top and bottom vsurfaces with respect to saidactuating member;

v5. In asnap action `electric switch, a movable switch member comprisinga pair of fiat integral U-shaped strips o'f resilient .material disposedin coplanar side by side relation to provide inner and outer pairs ofarms, means interconnecting said pair of inner arms at their open ends,means fixedly mounting said switch member at the open ends of said pairof outer arms, spring means connected to the .interconnected ends ofsaid inner arms to place said inner arms in compression and said outerarms in tension thereby to provide separate overcenter operations ofsaid inner arms with respect to said spring means and with respect tosaid outer arms, and a movable switch contact mounted upon said switchmember near the bight of at least one said U-shaped strip.

6. In a snap action electric switch, a movable switch member comprising.a pair of flat integral U-shaped strips ofresilient material disposedin coplanar side by side relation to provide inner and outer pairs ofarms, insulating means physically interconnecting but electricallyisolating said pair of -inner arms at their open ends, means fixedlymounting said switch member at the open ends of said pair of outer arms,spring means connected to the interconnected ends of said inner arms toplace said inner arms in compression and said outer arms in tensionthereby lto provide separate overcenter operations of said inner Varmswith respect to said spring means and with respect to said outer arms, apair of spaced apart movable s-witch contacts mounted upon said switchmember near the bights of said U-shaped strips, and a pair of stationaryswitch contacts fixedly mounted in cooperating relationship withsaidmovable switch contacts.

7. In a snap action electric switch, an enclosure having a heightdefined by substantially fiat parallel top and bottom surfaces, amovable switch member located within said enclosure and comprising apair of dat integral U-shaped strips of resilient material disposed incoplanar side by side relation to define generally a plane paralleltoand equidistant between said top and bottom surfaces and to' provideinner and outer pairs of arms, means interconnecting said pair of innerarms at their open ends, means xedly mounting said switch member in saidenclosure at the open ends of said pair of outer arms, a movableelongated member connected to the innerconnected ends of said inner armsand disposed in parallel relation between said inner arms, actuatingmeans connected to said elongated member for supplying a force toystress said elongated member and outer arms in tension and said innerarms in compression, said actuating means being movable in a transversedirection to initiate separate overcenter operations of said inner armswith respect to said elongated member and with respect to said outerarms, at least one stationary switch contact mounted in said enclosure,and a cooperating movable switch contact mounted upon said switch membernear the bight of at least one said U-shaped strip for snap actionmovement into or out of engagement with said xed switch contact, thedirection of movement of said movable switch contact in response tomovement of said actuating means in a given direction being selectableby locating said enclosure in alternate, reversed positions with respectto the given direction of movement of said actuating means.

References Cited in the file of this patent UNlTED STATES PATENTS2,306,794 Mustee Dec. 29, 1942 2,476,045 Kaminky July l2, 1949 2,582,034Hausler Jan. 8, 1952 2,630,504 Burch et al. Mar. 3, 1953

